Solid-state batteries show promise

November 24, 2019 07:59 PM

HANS GREIMEL

Toyota plans a big-time debut for solid-state batteries at the Tokyo Olympics next summer. A vehicle with solid-state batteries is expected to be driven in either the games’ opening or closing ceremonies.

When the gull-wing doors raised on the swoopy Lexus LF-30 Electrified concept car during its Tokyo Motor Show debut late last month, two words in bright blue letters could be seen on the car's threshold: "Solid State."

It was further evidence that Toyota is on track to keep a promise it made in 2017 to have solid-state batteries on the road by the mid-2020s.

These batteries use solid materials not only for the electrodes, but also for the electrolyte, normally a liquid or gel.

According to news reports, Shigeki Terashi, chief technology officer, told reporters before the Tokyo show that next year, Toyota will debut at the Tokyo Olympics a people-mover concept vehicle powered by solid-state batteries. Toyota, he said, expects solid-state batteries to begin mass production around 2025.

In the race to replace lithium ion in the next generation of electric car batteries, solid-state technology is gaining a lot of traction, not only at Toyota Motor Corp., but also with many other major automakers and battery suppliers, such as Japan's Panasonic Corp. and South Korea's LG Chem. Solid state just may have the magic formula that enables an almost seamless transition from internal-combustion engines to electric motors. Researchers know that to essentially replace gasoline the future electric car battery — regardless of its chemistry — must:

Have immense power and density

Be capable of ultrafast recharging
Dramatically reduce the danger of fires
Last the life of the vehicle
Cost far less than lithium ion does today

Affordably scale up to high-volume production.

Battery Basics

Anode: A positively charged electrode
Cathode: A negatively charged electrode
Cell: An individual battery that is part of a pack
Dendrite: A growth inside a ?lithium battery, sort of like a whisker, that can cause short circuits. The growths can poke through a battery's separator and cause the battery to fail.
Electrolyte: The medium inside a battery that enables ions to flow between the positive and negative electrodes. The electrolyte can be liquid, solid or gel.
Electrode: Transports electrons from one side of the battery to another to produce electrical current
Energy density: The amount of energy a battery can store in relation to its size or mass. Density determines the distance an electric car can travel between charges.
Lithium: A highly reactive metal inside the battery. Lithium ions move from the negative electrode to the positive electrode and back again.
Pack: A group of individual batteries connected in series. A Tesla Model S with an 85-kilowatt-hour battery pack has 7,104 individual cells.
Power density: The amount of power a battery can store in relation to its size. A battery with high power density enables a vehicle to accelerate very quickly but does not help it go farther between charges.
Thermal runaway: When a cell in a battery pack overheats and causes other cells to overheat beyond the ability of the vehicle's cooling system, possibly leading to a fire.

"Certainly, the game has changed now," Joe LoGrasso, a director at the United States Advanced Battery Consortium, told Shift. "The Koreans and Japanese have a lot of development that looks promising. It's now a global race to get to the best solution."

Solid-state batteries appear to have the best potential to meet most of the objectives for a next-generation battery, experts say. More lab work tweaking the chemistry and more real-world testing will determine whether they really do have the right stuff.

In an interview with Bloomberg published last month, M. Stanley Whittingham, one of the three men awarded this year's Nobel Prize in chemistry for their work on lithium ion, acknowledged the potential of solid-state batteries but said he expects lithium ion to remain dominant for at least the next decade.

"Toyota Motor Corp. and a whole host of American companies are working on solid-state batteries, though it's not clear how much those will cost to manufacture, and it's not clear yet whether you'll get a decent amount of power. They may work for things like iPhones initially, but there are some big questions before they are used in larger-scale systems," he said.

General Motors is one of the U.S. companies working on solid state. During a Shift conference on batteries last month at Lawrence Technological University in suburban Detroit, Tim Grewe, director of GM's global electrification and battery systems, said GM is bullish on solid-state batteries.

"Solid state for me comes in two categories — electrolyte and anode. Both of them haven't earned their way in yet," Grewe said during a panel discussion, "but we are very encouraged with them, to say they offer better range and less mass. They look very promising, and we are developing those as fast we can."

Solid-state batteries, such as this one from Toyota, use solid electrolyte rather than a liquid or gel.

But GM, Toyota, Honda Motor Co., other automakers and battery suppliers are also working on improving lithium ion batteries. And while solid-state batteries have great potential, Whittingham says there is still plenty of efficiency left to be gained by improving the chemistry of lithium ion batteries. "Right now, we only get 25 percent of theoretical capacity of them, so that's 75 percent that's dead volume or dead weight," Whittingham told Bloomberg. "It's the top folks in the world working on that project."

LoGrasso said: "As we look at the next generation of lithium ion batteries, they are going to include more nickel content in the positive electrode. We'll start adding more silicon to deal with fast-charging in the negative electrode. There is a lot of research going on into less flammable electrolytes to try to deal with the flammability threat."